Incremental printing of symbolic information – Light or beam marking apparatus or processes
Reexamination Certificate
2000-06-27
2003-03-04
Pham, Hai (Department: 2861)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Reexamination Certificate
active
06529228
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a laser working method for example a method for producing by such a laser working method an ink jet recording head for discharging an ink droplet and depositing such ink droplet on a recording medium, and an ink jet recording head produced by such a method. In particular, the present invention relates to a laser working method capable of working a worked article without fusion or thermal expansion therein and capable of precisely working a fine mask pattern in mask projection, a method for producing an ink jet recording head by such a laser working method, and an ink jet recording head thus produced.
2. Related Background Art
For minute working of a structured article requiring a fine structure and high precision, a laser working method employing an ultraviolet laser has been employed.
Such minute working can be exemplified by working of ink flow paths and ink discharge ports of an ink jet recording head.
The Japanese Patent Application Laid-Open No. 2-121842 or No. 2-121845 discloses high precision working of forming ink flow paths and ink discharge ports with an excimer laser which is a representative ultraviolet laser.
The excimer laser is capable of emitting ultraviolet light of a short pulse (15 to 35 ns) by discharge excitation of mixed gas of rare gas and halogen gas, with an oscillation energy of several hundred mJ/pulse and a pulse repeating frequency of 10 to 500 Hz. When the polymer resin surface is irradiated with a short-pulsed ultraviolet light of such high intensity, there is generated an ablative photodecomposition (APD) process in which the irradiated portion instantaneously decomposes and scatters with a plasma light emission and an impact sound, whereby so-called laser ablation working of polymer resin is made possible.
Among the conventional lasers employed for such working, the widely employed YAG laser can form a hole, but generates a coarse edge face, while the CO
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laser emitting infrared light is associated with a drawback of generating a crater around the formed hole. Such laser working methods are thermal working methods in which the working is achieved by converting optical energy into thermal energy, so that the shape of the worked article is often lost and fine working is difficult to achieve. On the other hand, the laser ablation working utilizing the excimer laser, based on sublimation etching by a photochemical reaction breaking the covalent bond of carbon atoms, does not easily break the shape of the worked article and can therefore achieve working of very high precision.
The laser ablation working method means a working method by sublimation, not through a liquid phase, by a laser.
Particularly in the field of ink jet technology, it is fresh in memory that the technology has undergone a remarkable progress to the present state by the adoption of the laser ablation working technology utilizing such excimer laser.
With the practical adoption of such laser working technology with excimer laser, there have been found the following phenomena.
The pulse oscillation time of the irradiating laser is about several ten nanoseconds in case of the excimer laser which is an ultraviolet laser or about 100 picoseconds to several nanoseconds in case of the YAG laser, but all the laser light falling on an article is not consumed for cleaving the covalent bonds of the atoms.
Because of the presence of such optical energy not consumed in cleaving the covalent bonds of the atoms, the laser worked portion of an article scatters before being completely decomposed, thereby forming by-products around the working area.
A part of the optical energy not consumed in cleaving the covalent bonds of the atoms is converted into thermal energy.
Also, as the energy density of the excimer laser remains at the level of 100 megawatts at maximum in the oscillation pulse, the subliming ablation working is not easily applicable to the materials of high thermal conductivity such as metals, ceramics or mineral substances (such as silicon) or materials of low light absorption such as quarts or glass, and can be principally employed for organic resinous materials.
These phenomena are unavoidable in using the excimer laser, and various technologies have been proposed to avoid the influences of these phenomena on the actual ink jet head.
For example a step of removing the by-products is executed, since the ink discharge ports may be clogged if the ink jet recording head is assembled while such by-products still remain.
Also, as the conversion of part of optical energy into thermal energy may cause thermal expansion or partial fusion of an article in the course of working, a material of a high glass transition point or a reduced working pitch is employed.
Since these technologies do not fundamentally resolve these phenomena, various limitations are practically imposed in the laser working.
On the other hand, a higher definition in the image quality is being required for the ink jet recording head, and the density of arrangement of the ink discharge ports or the ink flow paths, which has conventionally been in a range of from 300 to 400 dpi, is now required to be increased to 600 dpi, or even 1200 dpi.
Therefore, there is a demand for a method capable of forming the discharge ports and the ink flow paths with a small pitch or a small dimension, such as an arrangement pitch of 50 &mgr;m or less and a working diameter of 20 &mgr;m or less, with a high precision.
However the above-mentioned phenomena associated with the excimer laser become more conspicuous as the working pitch or the working diameter becomes smaller, and are posing limitations in producing the ink jet head of high precision as mentioned above.
In consideration of the foregoing, the present inventors, having recognized that the aforementioned phenomena are ascribale to the laser ablation working utilizing the ultraviolet laser exemplified by the excimer laser, have made intensive investigations not restricted in the field of the conventional technologies and have reached a novel laser ablation technology that is capable of fundamentally resolving these phenomena, also adapting to the minute working technologies ever advancing hereafter and also expanding the adaptability to various applications.
SUMMARY OF THE INVENTION
The present invention was made in view of the foregoing. An -object of the present invention is to provide a laser working method free from generation of by-products and fundamentally avoiding accumulation of thermal energy, generated in the course of laser working, in an article such as a resinous material (generally called “workpiece”), thereby achieving highly precise working without fusion or thermal expansion of the article, a method for producing an ink jet recording head utilizing such laser working method, and an ink jet recording head produced by such producing method.
Another object of the present invention is to provide a laser working method capable of forming a minute structure in an article composed of plural materials by a simple working step, a method for producing an ink jet recording head utilizing such laser working method, and an ink jet recording head produced by such producing method.
Still another object of the present invention is to provide a laser working method capable of simplifying an alignment step, improving the precision such as the positional precision of an internally structured member and reducing the manufacturing cost, a method for producing an ink jet recording head utilizing such laser working method, and an ink jet recording head produced by such producing method.
Still another object of the present invention is to provide a laser working method capable of improving the working efficiency by constructing an article so as to absorb the radiation energy of laser, a method for producing an ink jet recording head utilizing such laser working method, and an ink jet recording head produced by such producing method.
The above-mentioned objects can be attained, according to the present inven
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Pham Hai
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